PROJECT SUMMARY Studies are showing that more Americans are drinking alcohol, and problematic high-risk drinking is particularly on the rise in women, racial minorities, and older adults. Likewise, obesity has become extremely prevalent in the United States where more than 1 in 3 adults are considered to have obesity. What is more concerning is that obesity is on the rise in children and adolescents where 1 in 6 are considered to already have obesity. The full impact of this ?obese? generation has yet to be realized as they continue to age. Alcohol use and obesity represent two of the biggest risk factors for the development of cancer and neither shows any signs of subsiding in the United States in the near future. There is thus an urgent need to better understand the links between so-called Western diets, alcohol use and cancer. In our proposal, we put forth a novel hypothesis for explaining, at least in part, why high fat/high sugar diets and alcohol use are such major risk factors for cancer. We propose that these diets have a major impact on the availability and metabolism of acetate by cancer cells. Both alcohol and high doses of fructose (i.e. high fructose corn syrup, soda, sweet teas, etc.) generate substantial amounts of acetate in the liver and colon, respectively. Emerging research shows that the consumption and metabolism of acetate by cancer cells is necessary for tumor growth and progression. Indeed, acetate is avidly consumed by tumors, such that the more acetate you provide a tumor, the more it uses acetate to make acetyl-CoA. Mechanistically speaking, there is still much to be understood in terms of how and why acetate is an important nutrient source for tumors. Acetate-derived acetyl-CoA is an energy source for ATP production, a precursor for fatty acids, phospholipids and, by extension, membrane biogenesis, and finally acetate is a key post-translational signaling molecule when it is attached to histones via acetylation. Histone acetylation is a master regulator of gene transcription and both alcohol and Western diets have been shown to highly alter chromatin states in normal tissues. However, no one has ever investigated how dietary- induced changes in acetate metabolism impact tumor growth and progression. In this proposal we seek to understand the links between diet, acetate metabolism, the epigenome, and the microbiome (which is the major site of acetate production in humans) with respect to tumor growth and progression. We will address this gap in knowledge by applying genetically engineered mouse models of cancer, novel stable isotope tracing and mass spectrometry methods (including metabolomics and proteomics) combined with microbiota metagenomics and high dimensional multivariate data analyses to elucidate the mechanistic links between diet and cancer. Our ultimate goal is to use this information to identify opportunities for translation to new therapies. The sheer scope of alcohol use, obesity and cancer means our research will have a major and broad impact on these important health problems.